The present invention relates to a keyboard apparatus for an electronic musical instrument such as an electronic piano, electronic organ, or the like.
The applicants of the present invention have proposed a keyboard apparatus in Japanese Published Unexamined Utility Model Registration Application Nos. 149990/1990 through 149994/1990 and 149998/1990, as shown in FIG. 1. The keyboard apparatus for an electronic musical instrument comprises a metallic keyboard chassis 1, a balance rail 2 which is mounted on the keyboard chassis 1, pins 3 which are provided on the balance rail 2. The balance rail 2 and each of the pins 3 constitute a fulcrum 7 for a black key 5 and a white key 6, respectively. The fulcrum for the black key 5 is arranged in the same row as, or in front of (i.e., to the side of a player), the fulcrum for the white key 6. In the rear of each key, there is provided a hammer 8 which is caused to swing by the swinging of each key. In the arrangement of this keyboard apparatus, a force of inertia is given by the hammer 8 when the key is operated. By positioning the fulcrum, on the balance rail 2, for the black key 5 in the same row as, or in front of, the fulcrum for the white key 6, it is possible to give a feeling of mass to the black key 5 which is shorter in length than the white key 6, with a result that the feeling of key-touching at the time of playing can be improved. In FIG. 1, showing the prior art, numeral 9 denotes a front rail, numeral 10 denotes a guide pin, numerals 11a, 11b denote means for restricting the downward movement of the keys 5, 6 and which are provided in a front portion of the keyboard chassis 1, numeral 12 denotes a sound generating switch which is operated by a switch pressing member 13, numeral 14 denotes a weight, numeral 15 denotes a supporting member for the hammers 8, and numeral 16 denotes a holder for the keys. Numeral 17 denotes a hammer upper limit stopper which is made up of a metallic rail or a cushion provided in a rear portion of the keys and below the hammers 8 via a bracket 21 in order to restrict the swinging of the hammers 8. Numeral 20 denotes an upper limit stopper for restricting the upward swinging of the keys 5, 6.
(In the above and following descriptions, members such as the key and the hammer are referred to in a singular form as well as in a plural form. The member described in a singular form, due partly to linguistic limitations or reasons, is to be understood to include a plural form where necessary.)
Further, another prior art arrangement is known, as shown in FIG. 2, in which there is provided, above the keys 18, a rail 17 which extends in the lateral direction, i.e., in the direction in which the keys 18 are arranged. A rear upper end portion of each key 18 is thus made to abut the rail 17 to directly restrict the movement of the keys 18. Furthermore, as shown in the prior art FIG. 3, in a rear upper portion of each key 18, there is swingably disposed the hammer 8 with a capstan pin 19. It is thus so arranged that the swinging movement of the hammer 8 is restricted by the rail 17 which extends in the lateral direction, i.e., in the direction in which the keys are arranged.
In an ordinary keyboard apparatus for an electronic musical instrument, there is known a prior art apparatus as shown in FIGS. 7 and 8 in which each key 31 which is provided on a key bed 30 so as to be swingable about a fulcrum 7 is fixed in the following manner. Namely, a shaft 32, which extends upwards through the key bed 30 above the keys 31, is pulled down by a lever 34 to fix it by a rail 33 provided on the shaft 32. The keyboard apparatus is thus prevented from being damaged by the movement of the keys 31 through vibrations and shocks during transportation or movement of the electronic keyboard apparatus.
In the keyboard apparatus it is general practice to set the swinging distances of the black key and the white key substantially equal to each other so that the feeling of operation (i.e., depression or touching) of the keys does not vary between the black key and the white key. In the above-described keyboard apparatus, the distance from the fulcrum for the black key to the hammer 8 and the distance from the fulcrum for the white key to the hammer 8 are substantially equal to each other. Or else, the former is longer than the latter. It follows that the hammer 8 for the black key swings at a larger angle than does the white key. As a result, there is a disadvantage in that the dynamic feeling of touching the key varies from the black key to the white key. Further, in an electronic musical instrument in which a touch-detecting device, i.e., a device for detecting the touching of the hammers, is provided in the hammer 8, there is another disadvantage in that the detected values may fluctuate because the angle of rotation of the hammer 8 varies from the black key to the white key even with the same strength of touching or depressing the key.
In the conventional keyboard apparatus for an electronic musical instrument shown in FIG. 1, the distance or length of the key from the fulcrum backwards is set to be equal for both the black key and the white key. Since the black key and the white key are depressed by the same stroke, the rear end of the black key whose distance from the fulcrum forwards is shorter than that of the white key is, as shown in FIG. 4, lifted higher than the rear end of the white key 6 by the difference or distance L. However, if the rail 17 is provided as described above, the movement of the rear end of the black key 5 will be restricted in the course of the stroke. Due to this restriction, there is a disadvantage in that a difference in the feeling of touching is generated between the black key 5 and the white key 6. Further, since the keys are made of wood, they are subject to deformation due to environmental changes. As a result, there is a disadvantage in that their movements are similarly subject to deviations or fluctuations. In the apparatus shown in FIG. 3, if the length of the capstan pin 19 is adjusted so that the hammer 8 for the black key 5, for example, can be moved to the same height as that of the hammer 8 for the white key 6, the foregoing problem may be solved. However, the capstan pin 19 is expensive and, since it is mounted inside the mechanism, its adjustment is difficult. Since such an adjustment work is difficult in the rear or in the lower portion of the keyboard apparatus due to wiring and other mechanisms, it is preferable to position the adjusting members in an upper portion of the keyboard apparatus.
In a construction, as shown in FIG. 1, in which the entire keys are mounted on a single piece of keyboard chassis 1, there is a disadvantage in that, when the keys are long, the keyboard chassis 1 also becomes long accordingly, with the result that it becomes large in weight and high in cost. As a solution to this problem, an attempt was made to divide the keyboard chassis into the front and rear portions to directly mount them on the key bed. However, there was a disadvantage in that the assembling accuracy was poor with a small mechanical strength.
Furthermore, the applicants also earlier proposed an apparatus which has substantially the same construction as shown in FIG. 1 except that the position for mounting the hammer 8, which is provided to give the swinging of the key a force of inertia, is set to be a rear upper portion of the key, thereby minimizing the length, in the longitudinal direction of the keys, of the keyboard apparatus and facilitating the assembling of the hammer 8. In the resultant arrangement as shown in FIGS. 5 and 6, shafts 22, 22 of a substantially oval cross section are provided on both side surfaces of the hammer 8. In a stationary member 23, FIG. 5, which is fixed to the keyboard chassis 1, there are provided bearing recesses 24 which are substantially equal to the maximum diameter of the shafts 22, narrow guiding slots 25 for guiding the shafts 22 from outside into the bearing recesses 24, and a split slot or groove 26 for inserting thereinto the hammer 8. These shafts 22 and bearing recesses 24 constitute a fulcrum 27, FIG. 6, into which the hammer 8 can be fitted. The hammer 8 is thus introduced through the guiding slots 25 into the bearing recesses 24 to thereby swingably support the hammer 8 on the stationary member 23. The width of the guiding slots 25 is formed substantially equal to the minimum width of the shafts 22. In the keyboard apparatus in general, lateral vibrations or clattering of the hammers is not favorable because the feeling of key-touching is impaired. Therefore, in the arrangement shown in FIG. 5, it is necessary to make the clearance between the internal surface 28 of the split groove 26 of the stationary member 23 and the side surface 29 of the hammer 8 which abuts them, to a small value over the wide entire area of the clearance. However, since the hammers 8 and the stationary members 23 are made by resin moulding, casting, or the like, the mechanical finishing of the metallic moulds must be made in a very precise manner in order to minimize the clearance. This will result in a higher cost for manufacturing or machining the metallic moulds. If the above-described area of abutment or contact is minimized, the cost for machining the metallic mould may be reduced. Then, the lateral clattering cannot sufficiently be prevented, and extra members for preventing the lateral clattering will have to be provided, resulting in an extra trouble. This kind of problem of preventing the lateral vibrations or clattering also arises in directly supporting the keys on the stationary members.
In order to prevent the keys from being damaged due to vibrations while the electronic musical instrument is transported, if the rear upper portion of the keys 31 is held or pressed by the rail 33 which moves up and down as shown in FIGS. 7 and 8, there is a disadvantage in that the distance of vertical movement of the rail 33 must be kept large with the result that the keyboard apparatus becomes large in construction. This system is not suitable for a keyboard apparatus in which the hammers are provided in the rear upper portion of the keys.